The radio transmission of communications signals, for example, audio signals, is normally effected by one of two methods. In one, referred to as an amplitude modulation system, a sinusoidal radio frequency carrier is modulated in amplitude in terms of the intelligence or communications signal, and when the signal is received at a receiving location, the reverse process, that is, demodulation of the carrier, is effected to recover the communications signal. The other system employs what is termed frequency modulation, and instead of amplitude modulation of the carrier signal, it is frequency modulated. When an FM frequency modulation or FM signal is received, circuitry is employed which performs what is termed discrimination wherein changes in frequency are changed to changes in amplitude and in accordance with the original modulation, and thereby a communications signal is recovered. In both systems, there is as a basis a sinusoidal carrier which is assigned and occupies a distinctive frequency band width, or channel, and this channel occupies spectrum space which cannot be utilized by other transmissions within the range of its employment. At this time, almost every nook and cranny of spectrum space is being utilized, and there is a tremendous need for some method of expanding the availability of communications channels. In consideration of this, it has been suggested that instead of the use of discrete frequency channels for radio communications links, which is the conventional approach, a radio transmission link employing a wider frequency spectrum which may extend over a range of 10 to 100 times the intelligence band width being transmitted, but wherein the energy of any single frequency making up that spectrum be very low, typically below normal noise levels. Thus, it would be obvious that this type of transmission would be essentially non-interfering with other services. Making use of this approach, it has been proposed that coded sequence modulations be somehow employed and that each such communications link be non-interfering by virtue of different coded sequences, which would be turnable features.
Significantly, however, as far as the applicant is aware, no known practical systems has been as yet developed by others.
It is the object of this invention to extend the spectrum range of spread spectrum communications to operate in the range of approximately 1,000 to 1,000,000 or more rather than 10 to 100 times the intelligence modulation rate, and to accomplish this with an exceedingly simple and low cost electronic assembly.